What is grammage (GSM)? Paper weight in packaging explained

Grammage is the weight of paper per square metre, written g/m² and often shortened to GSM. Alongside size and print, it is one of the basic values in every quote for paper packaging, from bakery bags to carrier bags. If two quotes use the same size and grammage, both are priced on the same amount of paper; if the grammage differs, comparing unit prices side by side is misleading.

How is grammage measured?

Grammage is found by weighing a sample of known area; the laboratory method, including sample conditioning, is set out in ISO 536. For a quick check you cut a 10 × 10 cm piece of paper, which is 0.01 m². If the piece weighs 0.80 grams, the paper is 80 g/m²: you multiply the weight by 100. Any goods-in team with a scale reading to 0.01 g can run this check itself. Because one sample can mislead, take readings from several points and look at the average. The accepted deviation, the tolerance, belongs in the packaging specification before the order; we cover it in our article on packaging specification and tolerance.

What grammage is used for paper packaging?

Across our own product range, paper grammage spreads widely depending on the job the paper has to do:

• Wrapping and tray papers: 27–110 g/m²
• Flat bakery bags (window, greaseproof, natural kraft, white sulphite): 38–70 g/m²
• Block-bottom bags: 50–140 g/m²
• Paper bags with twisted, flat or die-cut handles: 70–110 g/m²
• Luxury paper bags: typically 170–250 g/m²

The low end covers papers that wrap a product or hold a light portion. The high end covers bags that carry weight and need to keep their shape. Grammage options and specifications for our twisted handle bags are listed on the twisted handle paper bags page.

Does a higher grammage mean stronger packaging?

Not always. Grammage tells you how much material the paper contains, while strength depends on fibre type, how the paper is made and how the packaging is built. Virgin kraft paper is usually stronger than recycled paper of the same grammage. In a carrier bag, carrying capacity depends on bag size, handle construction and how the load sits, as well as on grammage; that is why our product pages give capacity as “up to approximately 6 kg”, depending on those factors. Grammage is not thickness either: thickness, or caliper, is measured in microns and varies with paper density at the same grammage. Grease resistance comes from the paper type or treatment, not from the grammage. Grammage is also not the same as US basis weight, which is stated in pounds per ream and does not convert one to one.

How should grammage appear in a specification?

A specification states grammage as one value together with the paper type, for example “80 g/m² natural kraft” or “50 g/m² white sulphite”. A request that only says “kraft bag” leaves the choice of grammage to the supplier and makes the quotes hard to compare. The same line should carry the accepted deviation and whether recycled fibre is allowed. For paper in direct contact with food, ask for a declaration of conformity as well; grammage says nothing about food-contact compliance. When the sample arrives, the first check is to weigh it at several points and compare with the specified value.

Why does grammage matter when you buy packaging?

Grammage changes paper cost, packaging weight and weight-based fees directly. A simple worked example: if a bag uses 0.25 m² of paper, its paper weighs 20 grams at 80 g/m² and 25 grams at 100 g/m². That is 25 per cent more paper per piece, and on an order of 100,000 bags the difference reaches 500 kilograms. Extended producer responsibility schemes in Europe, including UK packaging EPR, charge by packaging weight and material, so an unnecessarily high grammage raises that line too.

On the quote side the rule is simple: a quote without a stated grammage cannot be compared with another. If one supplier prices 70 g/m² and another 90 g/m², the lower unit price often just reflects less paper. How to read each line of a quote is explained in our article on how to read a packaging quote. When you request a quote, tell us the product, its size and the load it has to carry, and we will suggest a grammage on that basis.